linux-kernel - Re: [PATCH] drm/msm: Grab the GPU runtime in a6xx routines, not the GMU one

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Message-ID: <f3b53f49-6e3f-3a3f-6737-d51a9d6ab78b@quicinc.com>
Date:   Thu, 9 Jun 2022 21:14:16 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Jordan Crouse <jordan@...micpenguin.net>
CC:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Chia-I Wu <olvaffe@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        "Eric Anholt" <eric@...olt.net>,
        Jonathan Marek <jonathan@...ek.ca>,
        Sean Paul <sean@...rly.run>, Wang Qing <wangqing@...o.com>,
        Yangtao Li <tiny.windzz@...il.com>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm: Grab the GPU runtime in a6xx routines, not the
 GMU one

On 6/9/2022 8:03 PM, Douglas Anderson wrote:
> >From testing on sc7180-trogdor devices, reading the GMU registers
">"  ??
> needs the GMU clocks to be enabled. Those clocks get turned on in
> a6xx_gmu_resume(). Confusingly enough, that function is called as a
> result of the runtime_pm of the GPU "struct device", not the GMU
> "struct device".
>
> Let's grab a reference to the correct device. Incidentally, this makes
> us match the a5xx routine more closely.
>
> This is easily shown to fix crashes that happen if we change the GPU's
> pm_runtime usage to not use autosuspend. It's also believed to fix
> some long tail GPU crashes even with autosuspend.
>
> NOTE: the crashes I've seen were fixed by _only_ fixing
> a6xx_gpu_busy(). However, I believe that the same arguments should be
> made to a6xx_gmu_set_freq() so I've changed that function too.
>
> Fixes: eadf79286a4b ("drm/msm: Check for powered down HW in the devfreq callbacks")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
>   drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 6 +++---
>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 4 ++--
>   2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index 9f76f5b15759..b79ad2e0649c 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -129,13 +129,13 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp)
>   	 * This can get called from devfreq while the hardware is idle. Don't
>   	 * bring up the power if it isn't already active
>   	 */
> -	if (pm_runtime_get_if_in_use(gmu->dev) == 0)
> +	if (pm_runtime_get_if_in_use(&gpu->pdev->dev) == 0)

Wouldn't we return early here when this fn is called from a6xx_gmu_set_initial_freq()?

-Akhil.

>   		return;
>   
>   	if (!gmu->legacy) {
>   		a6xx_hfi_set_freq(gmu, perf_index);
>   		dev_pm_opp_set_opp(&gpu->pdev->dev, opp);
> -		pm_runtime_put(gmu->dev);
> +		pm_runtime_put(&gpu->pdev->dev);
>   		return;
>   	}
>   
> @@ -159,7 +159,7 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp)
>   		dev_err(gmu->dev, "GMU set GPU frequency error: %d\n", ret);
>   
>   	dev_pm_opp_set_opp(&gpu->pdev->dev, opp);
> -	pm_runtime_put(gmu->dev);
> +	pm_runtime_put(&gpu->pdev->dev);
>   }
>   
>   unsigned long a6xx_gmu_get_freq(struct msm_gpu *gpu)
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 841e47a0b06b..87568d0b6ef8 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -1659,7 +1659,7 @@ static u64 a6xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
>   	*out_sample_rate = 19200000;
>   
>   	/* Only read the gpu busy if the hardware is already active */
> -	if (pm_runtime_get_if_in_use(a6xx_gpu->gmu.dev) == 0)
> +	if (pm_runtime_get_if_in_use(&gpu->pdev->dev) == 0)
>   		return 0;
>   
>   	busy_cycles = gmu_read64(&a6xx_gpu->gmu,
> @@ -1667,7 +1667,7 @@ static u64 a6xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
>   			REG_A6XX_GMU_CX_GMU_POWER_COUNTER_XOCLK_0_H);
>   
>   
> -	pm_runtime_put(a6xx_gpu->gmu.dev);
> +	pm_runtime_put(&gpu->pdev->dev);
>   
>   	return busy_cycles;
>   }